The present invention relates to an image sensor and, more particularly, a method and apparatus for detecting and correcting values of defect pixels.
Generally, an image sensor is an apparatus to capture images using light sensing semiconductor materials. Since brightness and wavelength of light from an object are different in their amount according to the reflection area, electrical signals from pixels are different from one another. These electrical signals are converted into digital signals, which can be processed in a digital circuit, by an analogue-to-digital converter. Thus, the image sensor needs a pixel array having tens to hundreds of thousands of pixels, a converter for converting analogue voltage signals into digital voltage signals, hundreds to thousands of storage devices and so on.
Especially in the image sensor, it is a high quality of picture that determines competitiveness in the markets. However, as described above, since the image sensor needs a plurality of devices such as pixels, converters and so on, a possibility of errors may always exist in fabricating it. When the errors occur, the errors may appear such as spots and lines in the display. Furthermore, since an erroneous image sensor is considered as a device failure, yield may be dramatically reduced with the waste of resources.
It is, therefore, an object of the present invention to provide an image sensor, which can detect and correct values of defective pixels and then output a corrected data.
In according with an aspect of the present invention, there is provided an image sensor comprising: an error detection circuit for detecting an error by comparing difference between a current pixel value and a previous pixel value with a predetermined reference value; and an error correction circuit for correcting an error value from a pixel, by substituting the previous pixel value for the current pixel value.
The error detection circuit according to the present invention comprises a subtractor creating the difference between the current pixel value and the previous pixel value and a comparator for comparing an output from the subtractor with the predetermined reference value, wherein the predetermined reference value is stored in a programmable register. And the predetermined reference value is determined, based on characteristics of a light sensing area and an analogue-to-digital converter.
In accordance with another aspect of the present invention, there is provided an image sensor comprising: a control and interface means for controlling the image sensor using a state machine and for interfacing the image sensor with an external system; a pixel array including a plurality of pixels sensing images from an object and generating analogue signals according to an amount of incident light; a conversion means for converting the analogue signals into digital signals to be processed in a digital logic circuit; an error detection circuit for detecting an error by comparing difference between a current pixel value and a previous pixel value with a predetermined reference value; and an error correcting means for correcting an error value from the pixels, by substituting previous pixel values for current pixel values.